QUrl::toAce() returns non-empty string for some invalid inputs

The documentation for QUrl::toAce() says: "This function returns an empty QByteArray if domain is not a valid hostname", and yet it returns non-empty strings for some invalid stuff:

qDebug() << QUrl::toAce("xn--z.no");
---
"xn--z.no"

The test suite even checks this for some reason.